In an electrophotographic image forming apparatus, there has been known a structure in which elements such as a photosensitive drum and a developing roller as rotatable members contributable to image formation are integrated into a cartridge which is dismountable from a main assembly of an image forming apparatus main assembly (hereinafter, apparatus main assembly).
As one of the structures in which a cartridge is dismountably provided in such an image forming apparatus, there is also known a structure in which a toner cartridge containing toner (developer) to be consumed with image forming operation can be exchanged separately from the photosensitive drum and developing roller.
With such a structure, toner (developer) contained in the toner cartridge is supplied to a developing device including a developing roller and the like through a discharge port. In addition, in order to prevent the toner from leaking to the outside through the discharge port, an opening/closing member such as a shutter for opening and closing the discharge opening is provided.
For example, Japanese Laid-open Patent Application No. 7-199623 discloses a structure in which when a cylindrical toner cartridge (developer supply container) is mounted in the image forming apparatus main assembly, the shutter is opened by rotating the toner cartridge.